1. Technical Field
The present disclosure relates to the treatment of asbestos containing material (ACM) with a mineralizing agent using a method, system, and apparatus that increases the receptivity of the ACM to the mineralizing agent.
2. Description of the Related Art
Asbestos is a term referring to a family of historically useful fibrous minerals that most commonly belong to the serpentine and amphibole mineral groups including such species as chrysotile, crocidolite, amosite, and anthophyllite. More precisely referred to as “asbestiform minerals,” they are hydrated silicates that generally contain substituted iron, calcium, magnesium, and sodium in various proportions. The serpentine group of minerals that includes chrysotile, antigorite, and lizardite are all represented by the approximate composition: Mg3 [Si2 O5] (OH)4. Of these, chrysotile represents the majority of all asbestos minerals used for industrial and commercial purposes. There is substantial variation in mineral chemistry and physical characteristics of asbestiform minerals, but they all have similarities in basic structure that are typically modified because of variations in the concentrations of calcium, iron, magnesium, and sodium.
Asbestos has been used in thousands of products and in numerous workplaces. Although the harm caused by asbestos is not apparent at first, asbestos exposure can lead to serious, debilitating, and often fatal diseases. These include mesothelioma, asbestos lung cancer, and asbestosis. Usually, a period of 10 to 40 years or more passes before the asbestos victim exhibits the first asbestos disease symptoms. In the workplace, there is no “safe” level of asbestos exposure. For this reason, increased limitations and restrictions on asbestos use in commercial products, handling, and disposal have been and continue to be imposed in many countries around the world.
As a toxic mineral, various attempts have been made to render asbestos inert so that it can be safely handled and disposed. Attempts to destroy asbestos waste using heat alone to alter asbestos fiber chemistry have met with only limited success since asbestos fibers by their very nature are refractory and self-insulating. For example, chrysotile fibers have been reported to withstand temperatures up to 3000° F. for time periods of up to one-half hour. Since such a technique requires very high temperatures for fiber destruction, this approach has proved quite uneconomical.
Several vitrification (or melting) processes, such as plasma melting and joule heating, have shown success in destroying asbestiform minerals. However, these processes are energy intensive and require very expensive and complex equipment. Thus, vitrification processes, although capable of destroying asbestos waste, have not exhibited commercial viability.
Other methods that utilize reduced process temperatures and a variety of chemical additives have also been attempted. With one exception, they have also met with limited success. The process of “Mineralogical Conversion of Asbestos Waste” described in U.S. Pat. No. 5,096,692, which is incorporated by reference in its entirety herein, is the one sub-melting point process that has achieved commercial development. In that patent, asbestos waste is converted to non-asbestos products below the melting point by the combination of chemical additives and the application of heat.
During the commercial development of Mineralogical Conversion of Asbestos Waste, it was found that the time required to convert 100% of the asbestos fibers in the waste took longer than that which would be required for other competitive though less efficient processing methods. Processing times of up to 60 minutes were required to assure that all of the asbestos fibers in the waste experienced destruction. The processing time was substantially reduced by the System and Method for Accelerating the Conversion in Asbestos in the Process of Mineralogical Conversion covered by Patent Cooperation Treaty Application No. PCT/US2006/026018, which is incorporated by reference in its entirety herein, wherein the asbestos containing materials are broken or shredded into particles, the particles are treated with a mineralizing agent, and the particles are heated in a furnace. It is desirable to further reduce the processing time in order to enhance the commercial viability of this process for large scale commercial applications.